\tracingonline=2
\tracingcommands=2
\tracingmacros=2
\tracingrestores=2

\count10=20
\multiply\count10 30
\showthe\count10

% spaces and by
\count10=20
\multiply  \count  10  20
\showthe\count10

\multiply  \count  10  by 20
\showthe\count10

\multiply  \count  10by20
\showthe\count10

% dimen
\dimen0=10.5pt
\multiply\dimen0by0.4pt
\showthe\dimen0

\multiply\dimen0by0.1pt
\showthe\dimen0

\multiply\dimen0by0.3cc
\showthe\dimen0

\multiply\dimen0by"3FFFFFFFsp
\showthe\dimen0

\count1="7FFFFFFF
\multiply\count1by2
\dimen1=1\count1
\showthe\dimen1

% skip
\skip0=10.5pt plus 4pt minus 3fil
\multiply\skip0by0.4pt plus 1fil minus 4pt
\showthe\skip0

\multiply\skip0by0.1pt plus 2fil minus 4fill
\showthe\skip0

\multiply\skip0by0.3cc
\showthe\skip0

\multiply\skip0by"3FFFFFFFsp
\showthe\skip0

\count1="7FFFFFFF
\multiply\count1by2
\skip1=1\count1
\showthe\skip1

% muskip
\muskip0=10.5mu plus 4mu minus 3fil
\multiply\muskip0by0.4mu plus 1fil minus 4mu
\showthe\muskip0

\multiply\muskip0by0.1mu plus 2fil minus 4fill
\showthe\muskip0

\multiply\muskip0by0.3cc
\showthe\muskip0

\multiply\muskip0by"3FFFFFFFsp
\showthe\muskip0

\count1="7FFFFFFF
\multiply\count1by2
\muskip1=1\count1
\showthe\muskip1


% overflow
\count1=214748364
\multiply\count1by11
\showthe\count1

\count1=107374182
\multiply\count1by11
\showthe\count1

\dimen1=214748364sp
\multiply\dimen1by11sp
\showthe\dimen1

\dimen1=107374182sp
\multiply\dimen1by11sp
\showthe\dimen1

% errors
\multiply\par\relax

\count0=10
\multiply\count0by\relax
\showthe\count0

\end
